Interpretive data for breath
WEL: 20 ppm (8h TWA) - reduced in 2018
Other names: tetrachloroethylene,
This information sheet provides interpretation of breath solvent
values obtained using the Bio-VOC™ breath sampler. Further
information regarding the implementation of a biological monitoring
strategy can be found in HSE's 'Biological
monitoring in the workplace' booklet.
Samples should be taken pre-shift, next day towards the end of
the working week in a 'clean' area, such as medical room, office or
canteen. Refer to the Breath Sampling Guidance Sheet for details of
how to take samples.
Tetrachloroethene is poorly metabolised and stored in adipose
tissue and so even a single exposure can be detected for several
days after exposure. It is therefore likely that tetrachloroethene
will accumulate in the body during a working week.
A well-conducted field study of 32 workers over a working week
(1) showed that exposure to 50 ppm (TWA) of
tetrachloroethene would give rise to 7 ppm (290 nmol/l) of
tetrachloroethene in alveolar air when sampled 60 hours post
exposure. A physiologically based pharmacokinetic model
(2) confirmed this. The American biological exposure
index (3) is 3 ppm (125 nmol/l) for an 8h TWA of 25 ppm
. SCOEL recommend the guidance value for an exposure of 20
ppm (8h TWA).
HSL Bio-VOC™ sampler has been used in surveys of workers in the
dry cleaning industry and in determining environmental exposure to
- If breath tetrachloroethene levels are below 40
nmol/l, exposure is likely to be below the WEL. A
suggested biological monitoring is once yearly, providing no change
in working practices.
- If breath tetrachloroethene levels exceed 40
nmol/l, exposure may approach the WEL. Regular monitoring
(perhaps six monthly) is recommended to ensure that exposure
remains under control.
- If breath tetrachloroethene levels exceed 125
nmol/l, it is likely that tetrachloroethene exposure
exceeds the WEL over an 8 hour time weighted average. A routine
monitoring strategy is recommended, as is investigation of the
efficacy of control measures. Very high exposures of
tetrachloroethene can occur in the dry cleaning industry
during loading and unloading of the machines.
Other Biological Monitoring
Other means of biological monitoring include
tetrachloroethene in blood (for which there is also an
American and a SCOEL guidance value).
Tetrachloroethene can be absorbed by inhalation or skin
1. Monster A et al. (1983) Scand.J.Work.Environ.Health. 9
2. Leung H.W. (1983) Am.Ind.Hyg.Assoc.J. 53 (6) 369-374
3. Biological Exposure Indices 2016. American Conference of
Governmental Industrial Hygienists.
SCOEL/SUM/133 (2009). Recommendation of the
Scientific Committee on Occupational Exposure Limits for